1. Field of the Invention
The present invention relates to a building structure that provides supported fasteners for holding heavy exterior cladding, the fasteners extending through a thick thermally insulating layer and into a metal stud.
2. Introduction
Metal frame building structures are relatively common, particularly in commercial building construction. Metal frame building structures typically comprise a framework of metal studs, a thermally insulating layer on the exterior surface of the metal stud framework, an exterior cladding over the thermally insulating layer and fasteners that extend through the thermally insulating layer that attach the exterior cladding to the metal studs. One of the challenges with such a metal frame building structure is providing sufficient support to keep the fasteners from pivoting (hinging) under the weight of the exterior cladding and/or under the force of wind blowing against the exterior cladding. Pivoting of the fasteners cause the cladding to sag or shift over time. The fasteners are essentially cantilevers, or lever arms, extending from a metal stud to the exterior cladding. Longer fasteners correspond to longer cantilevers that have a greater tendency to pivot at the metal stud under the load of an exterior cladding with the portion of the fastener most remote from the metal stud displacing downward under the load of the exterior cladding and/or wind forces. Often pivoting of a fastener is accompanied with local deformation, or bending, of the metal stud where the fastener attaches to the metal stud. This is particularly true with heavy exterior claddings such as wire mesh covered with stucco, brick and stone. Over time, exterior cladding can shift or sag if the fastener pivots under the weight of the exterior cladding.
Building codes are requiring an ever increasingly thickness of thermal insulation on the exterior surface of above grade metal frame building structures in order to improve the thermally insulating character of the resulting wall structure. Thermally insulating layer thicknesses of five centimeters or more are becoming desirable in the building industry. Increasing the thickness of the thermally insulating layer provides the structure with better thermally insulating properties, which generally translates into a more energy efficient building. However, thicker thermally insulating layers require longer fasteners to connect the exterior cladding to the metal studs of the metal frame. Longer fasteners are longer cantilevers between the metal studs and exterior cladding, which makes stabilizing the position of the exterior cladding more challenging. In order to accommodate thicker thermally insulating layers in metal frame building structures there must be some way to reinforce the fasteners from pivoting under the weight of the exterior cladding. Ideally, it is desirable to discover a way to reinforce the fasteners without compromising the thermal insulation property of the thermally insulating layer (for example, by increasing the density of the thermally insulating layer material or increasing the dimension or number of fasteners penetrating through the thermally insulating layer).